Articles having a structure of nanometer sized pores or voids can be useful for applications based on optical, physical, or mechanical properties provided by their nanovoided composition. For example, a nanovoided article includes a polymeric solid network or matrix that at least partially surrounds pores or voids. The pores or voids are often filled with a gas such as air. The dimensions of the pores or voids in a nanovoided article can generally be described as having an average effective diameter which can range from about 1 nanometer to about 1000 nanometers. The International Union of Pure and Applied Chemistry (IUPAC) have provided three size categories of nanoporous materials: micropores with voids less than 2 nm, mesopores with voids between 2 nm and 50 nm, and macropores with voids greater than 50 nm. Each of the different size categories can provide unique properties to a nanovoided article.
Several techniques have been used to create porous or voided articles including, for example, polymerization-induced phase separation (PIPS), thermally-induced phase separation (TIPS), solvent-induced phased separation (SIPS), emulsion polymerization, and polymerization with foaming/blowing agents. Often, the porous or voided article produced by these methods require additional process steps, such as a washing step, to remove materials such as surfactants, oils, or chemical residues used to form the structure. The washing step can limit the size ranges and uniformity of the pores or voids produced. These techniques are also limited in the types of materials that can be used. There is a need for a rapid, reliable technique for producing nanovoided articles that does not require a washing step.